Varnish is a very popular HTTP accelerator. One of its key features is caching.

When dealing with caching, it is always tricky to do correct Time To Live estimations. Especially when the trade-off is caching efficiently versus serving fresh content. To tackle that issue, you can invalidate cache entries via purging.

How Varnish does it

In the Varnish API there is a function called purge_url. It accepts a URL pattern as an argument and purges it. On the next hit the purged item gets replaced with the corresponding fresh content.

There are

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